Trogloraptor spider discovered deep in Pacific Northwest

A team of scientists and cave conservationists recently discovered a large, unique spider in caves and forests deep in the Pacific Northwest. 

Researchers were prompted to recognize the Trogloraptor as a new family of spider due to the arachnid’s “novel combination” of evolutionary features.

Indeed, the forests of the coastal regions from California to British Columbia are well known for their unique and ancient animals and plants, such as coast redwoods, tailed frogs, mountain beavers – and now, a large, newly discovered spider. 

Trogloraptor (or “cave robber”) is named for its cave home and spectacular, elongated claws. It is a spider so evolutionarily special that it represents not only a new genus and species, but also a new family (Trogloraptoridae).

Even for the species-rich insects and arachnids, to discover a new, previously unknown family is quite rare.


Trogloraptor hangs beneath rudimentary webs beneath cave ceilings. It is about four centimeters wide when its legs are extended — larger than the size of a half-dollar coin. Its extraordinary, raptorial claws suggest the spiders are fierce, specialized predators, but their prey and attack behavior remain unknown.


The anatomy of Trogloraptor has forced arachnologists to revise their understanding of spider evolution. Strong evidence suggests Trogloraptor is a close relative of goblin spiders (Oonopidae), but Trogloraptor is also equipped with a mosaic of ancient, widespread features and evolutionary novelties.


The true distribution of Trogloraptor remains unknown. Moreover, the fact that such a relatively large, peculiar animal could elude discovery until 2012 suggests more undiscovered species may be lurking in the dark forests and caves of western North America.